Strong anion exchange for improved NiCo2S4 oxygen reduction reaction via interlayer spacing manipulation

Transition metal sulfides as high-performance, cost-effective, and stable electrocatalysts for oxygen reduction reaction (ORR) have attracted much attention. The replacement of sulfur atom by oxygen atom in metal sulfides was considered to be the fundamental reason for its decreased activity. Adequate anion exchange can greatly reduce the generation of oxygen species in transition metal sulfide, which further enhances the intrinsic electrical conductivity and stability of transition metal sulfides. Herein, a novel and simple approach to larger interlayer spacing was provided by introducing interlayer water in layered hydroxides precursor. The NCS-O1 with treated layered hydroxides precursor exhibits few oxygen impurities and excellent activity for the ORR in alkaline electrolyte, presenting the close limiting diffusion current density and lower Tafel slope (reaches 56 mV dec−1, vs. Pt/C 70) in comparison to 20% commercial Pt/C. Hence, our results provide an interesting design path for such catalysts.